Back in 1929, Col. Charles Lindbergh -- the same aviator who, two years before, had become famous by flying solo across the Atlantic Ocean -- was flying a Pan American Airways plane from Miami to Panama when he decided to do a little sightseeing. Over what is now Belize, Lindbergh abruptly veered inland and flew over a stretch of southern Mexico and Central America that was covered with dense vegetation -- a region so remote and inaccessible that outsiders reportedly had never ventured there. As Lindbergh soared over the trees, something ahead caught his attention -- what an Associated Press account later described as "two emerald eyes staring up at him, out of the tangle of the jungle brush."

As Lindbergh swooped in low to investigate, he was astonished. It was the ruins of a vine-enshrouded city about 8 miles (12.8 kilometers) in diameter, dotted with numerous small pyramids and a 250-foot-tall (76-meter) stone temple with twin reflecting pools -- the green reflection that had looked to him like a pair of eyes. But there were no signs of humanity anywhere around the site. Lindbergh was filled with awe, as he gazed upon the ruined grandeur of a once-mighty Mayan city whose builders apparently had abandoned it to be swallowed up by the jungle [source: Associated Press].

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Why? That's a question that that archaeologists, scientists and historians have been puzzling about for decades. During their heyday -- about 250 AD to 900 AD -- the Mayans had one of the most advanced civilizations on the planet. They built more than 40 cities across Central America, filled with temples and palaces and elaborate sculpture and carvings whose magnificence still impresses. They developed advanced irrigation techniques for growing crops, and performed astronomical observations that enabled them to predict solar eclipses. They had a written language of hieroglyphs, which they used to write books on paper made from fig trees. They devised an elaborate calendar, whose cycles ran for centuries into the future [source: Britannica].

And yet, by the time Spanish conquerors arrived in Central America in the early 1500s, the great Mayan cities were empty, and the builders' descendants had reverted to a simple agrarian small-village lifestyle. Over the years, scholars have developed numerous theories about why the mighty Mayan culture collapsed, but recent discoveries point to a cause that sounds eerily familiar -- climate change. In this article, we'll take a look at whether Mayan civilization was undone by weather, and what lessons that might hold for our civilization today.

Theories About the Mayan Collapse

Unlike other vanished civilizations, at least some of the Mayans' written records have survived, which has enabled scholars to partially reconstruct their history. But those tantalizing clues have only made the mystery of their decline more frustrating [source: Diamond]. Over the years, researchers have developed various theories about what caused the decline of Mayan civilization. Here are three of the most prominent ones:

Over-farming. Some scholars have argued that Mayan society grew too rapidly for its own good. As the population increased, it put farmers under more and more pressure to grow food, and gradually, they ran out of fresh forest land to clear. That would have forced them to plant crops in their fields without an adequate fallow cycle -- that is, the time that it takes soil to rebuild its nutrient supply [source: McKillop].

Warfare. The Mayan rulers, who convinced their population that they were powerful enough to control the weather, may have started to believe their own hype. Their efforts to conquer neighboring peoples may have backfired, as long periods of war sapped Mayan resources and led to retaliation. There's evidence that a number of Mayan cities eventually were besieged and fell to invaders [source: McKillop].

Disease. In a 1979 article, researcher James L. Brewbaker theorized that Mayan society collapsed due to disease -- not a human epidemic, but an agricultural one, maize mosaic virus, which destroyed their food supply [source: Brewbaker].

While scientists aren't completely discounting all those possibilities, in recent years they've added another theory. Increasingly, they suspect that Mayan society collapsed because of the stress of climate change -- a risk that faces modern civilization today, as we burn huge amounts of fossil fuels and spew greenhouse gas emissions that warm the planet. The Mayans, though, didn't have gas-guzzling SUVs, and they didn't need coal-burning power plants to power their big-screen TVs and air conditioners, since they didn't have those either. So what was the deal with them? We'll look at possible explanations in the next section.

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Mayan Rain Rituals

Rituals to summon rain, reminiscent of the ones used by the ancient Mayans, are still performed in the Yucatan. In the ch'a-chak or "bring rain" ceremony, a shaman builds an altar to serve as a portal between this world and the next, through which the rain gods, or chakob, can be summoned. Over a three-day period, the chakob are offered corn bread, incense, stewed meats and honey wine as inducements. In the culmination, the shaman consumes a large amount of sugarcane brandy and enters a trance-like state, during which he supposedly communicates with the spirits. A researcher wrote about it in a 1997 article, noting that "shortly after the ceremony, we heard the deep rumble of thunder" [source: Schuster].

Scientists who've studied mineral deposits left by dripping water in caves have been able to construct a 2,000-year-long history of weather patterns in Central America. In an article published in Science in 2012, the researchers revealed that for the first several hundred years of Mayan civilization, the Mayans benefited from unusually wet weather that made it easier to grow crops, and enabled the Mayan population to expand. That also made the Mayan kings look pretty good, because they could claim credit for conducting the blood sacrifices and other rituals that kept the rains coming [source: Zabarenko]. (It's hard to say whether or not they really believed in their own magical powers.)

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But around 660 AD, the weather changed, and rain became more infrequent. That probably created a lot of tensions in Mayan society, because "they're doing the ceremonies and nothing's happening," Pennsylvania State University anthropologist Douglas Kennett explained in a 2012 interview with Reuters [source: Zabarenko].

Additionally, the Mayans also may have accelerated climate change by cutting down the forest around them, probably for fuel and to create wood plaster for use in their ornate buildings [source: Diamond]. From studying pollen found in ancient layers of Central American lake sediment, scientists learned that around 800 AD, about a century before the Mayan civilization began to crumble, tree pollen disappeared almost completely and was replaced by pollen from weeds. That suggested that the region's forests had all but disappeared.

Without trees and their root systems to keep soil in place, erosion would have worsened, carrying away fertile topsoil, which would have crippled Mayan agriculture. Additionally, trees function as natural air conditioners, drawing water through their leaves and cooling the local air when the water evaporates [source: U.S. Forest Service]. You can experience this same effect if you live in a city. In a park with trees, it's going to seem cooler than it does out in a city block with just buildings and asphalt all around. Computer simulations indicate that the region's temperature would have increased by as much as 6 degrees Fahrenheit [source: NASA].

That change would have been enough to alter the weather even more. Researchers who've analyzed changes in river sediment have found that in the century after deforestation, rainfall declined, with intense multi-year droughts occurring around 810, 860 and 910 AD [source: Haug, et al.].

Since the Mayans probably depended upon rain captured in reservoirs for drinking water, they would have faced not only hunger, but thirst as well [source: NASA]. It's not hard to imagine how a panicked Mayan population would have fled their once-great cities, as their way of life collapsed into a pre-Columbian version of "Mad Max." In the next section, we'll talk about whether their plight should be a warning to us.

Is There a Warning in the Mayan Collapse?

Teenage boys dressed as ancient Mayan warriors. What lessons does the decline of Mayan civilization hold for us today?

You've probably heard the claims that the Mayan calendar prophecies the end of the world in 2012 -- an idea that for some reason is tremendously appealing to modern-day apocalypse junkies, even though it's totally incorrect. Here's the 411: While December 21, 2012 corresponds to the end of a Mayan calendar cycle, the calendar calls for another cycle to begin immediately after that [source: Wolchover].

That said, there are some lesson from the Mayan collapse that we ignore at our own peril. Scientists worry that we are repeating the same pattern of deforestation that may have exacerbated climate change in Central America more than a millennium ago, except on a far more massive scale. Trees are about 50 percent carbon, and in the U.S alone, they presently absorb between 1 and 3 million metric tons (984,206 to 2,952,691 tons) of atmosphere-warming carbon dioxide, which offsets between 20 and 46 percent of what Americans spew into the atmosphere by burning coal and gasoline. But when we cut down trees or burn them, they release their stored carbon into the atmosphere, and they aren't around to absorb any more of it [source: Johnson].

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Over the past several centuries, the U.S. has cut down about 90 percent of the forests that once covered the continent, and what remains is still in peril. In the Pacific Northwest, for example, about 80 percent of the old-growth forestland is slated for eventual logging [source: University of Michigan]. Worse yet, in nations in the developing world -- Latin America, the Caribbean, Africa, and Asia -- once-lush forests have been disappearing at an alarming rate, thanks to logging, agriculture, and need for living space. In recent years, there's been some international progress in slowing the rate of deforestation, but we still face the risk that it will push us even faster into climate chaos [source: Johnson]. It's a problem that we must work harder to solve.

Author's Note: Did the Mayan Civilization End Because of Climate Change?

When I was researching this article, what fascinated me the most was reading old newspaper stories about Charles Lindbergh and other early 20th century explorers who searched for ancient Mayan cities in the Central American jungle. There was a thrilling, Indiana Jones sort of quality to these accounts, as the searchers ventured into remote areas where outsiders had never visited, at least not in the memory of that time. Today, sadly, there's precious little unexplored territory left on the planet, so the chance of anyone having such an adventure -- or of making such an incredible discovery -- is exceedingly remote.